The objectives of the proposed research are two fold, 1) to examine the role of the two limiting membranes on the control of corneal thickness, and 2) to measure in vitro and in vivo the relative roles of transport and hydrostatic pressure in the formation of aqueous humor. In more detail, 1) will involve the accurate measurement of the movement of ions, water and organic molecules across both the epithelium and endothelium to establish whether or not an active transport system exists which is involved in the maintenance of corneal thickness. Determinations will be made of drug penetration into and through the cornea as a function of the drug vehicle. 2) Recent evidence has shown that filtration is a very important component of aqueous formation. The studies will involve the measurement of ion and organic molecule fluxes across the isolate ciliary body to completely characterize the membrane in terms of membrane phenomena. In vivo experiments will reveal these characteristics in the living eye, as well allowing determinations to be made on the mechanism of aqueous formation. Several other parameters of aqueous formation will be measured in the living eye.